Using Viral Load Data to Monitor HIV Burden and Treatment Outcomes in the United States
February 7, 2012
Reporting viral load and CD4 counts is a critical first step in calculating community viral load -- a key action step called for in the National HIV/AIDS Strategy.1 In August 2011, the Centers for Disease Control and Prevention (CDC)2 released Guidance on Community Viral Load: Measures, Definitions, and Methods for Calculation to describe the concept of community viral load and provide definitions of and methods for calculating community viral load and related measures. The Guidance proposes common language for viral load (VL) measurements, which include four measures of viral load for an HIV-infected population. The HIV-infected population can be described by five component measures, depending on what information is available on the level of care, viral load, and diagnosis.
The following table shows the four VL measures and their corresponding population component measures:
|Viral Load Measures|
| ||Component Measures|
|Population Viral Load||In care with undetectable VL||In care with detectable VL||In care, no VL*||Diagnosed but not in care||Undiagnosed|
|Community Viral Load||In care with undetectable VL||In care with detectable VL||In care, no VL||Diagnosed but not in care|| |
|In-Care Viral Load||In care with undetectable VL||In care with detectable VL||In care, no VL|| || |
|Monitored Viral Load||In care with undetectable VL||In care with detectable VL|| || || |
* No VL = missing/unknown, for a variety of reasons (e.g., incomplete reporting).
Estimating Measures of Viral Load
- Population Viral Load: This is the most comprehensive measure;
however, it is a conceptual measure, which cannot be directly
- Community Viral Load: At this time, calculation is not feasible
for most jurisdictions. For jurisdictions to be able to estimate
this measure, they would need to address missing VL data among
residents with an HIV diagnosis or obtain data by increasing testing
and maximizing linkage to, and retention in, care. Imputing data for
diagnosed cases with missing VL data would require supplemental data
that are not available in most areas. Valid information on current
address is required for residents with an HIV diagnosis to ensure
that persons no longer residing in the area are excluded from the
- In-Care Viral Load: At this time, calculation is not feasible
for most jurisdictions. For jurisdictions to be able to estimate
this measure, they would need to address missing VL data to maximize
the proportion of persons in care who have VL data in the HIV
surveillance system. Imputing data for diagnosed cases with missing
VL data would require supplemental data, such as antiretroviral
therapy data, that are not available in most jurisdictions.
- Monitored Viral Load: Most jurisdictions can calculate this
measure for residents with an HIV diagnosis.
Additionally, standardized categorical measures have been defined and
can be used to assess the quality of HIV care or the possible
transmission potential for the HIV-infected population that is receiving
- Suppressed/not suppressed (where ≤200 copies/mL is suppressed
and >200 copies/mL is not suppressed)
- Undetectable VL (≤50 copies/mL)
- High VL (>100,000 copies/mL)
Ability of Surveillance Programs to Calculate Viral Load Measures
Using viral load measures to monitor HIV burden and treatment
outcomes does not rest solely with the HIV surveillance system; rather,
taking steps to ensure that these measures can be calculated is a
function of policy, care and treatment (practice), and surveillance.
- HIV treatment guidelines (when/how often VL test recommended).
- Reporting policies for laboratory tests, which vary by
- Sharing of surveillance data within and across jurisdictions.
- Reporting of data to surveillance programs (private and federal
facilities and institutions).
- Practice of requesting VL tests (health care providers).
- Practice of reporting VL data (laboratories).
- Reach of HIV testing and linkage to care programs.
- Entering/uploading of laboratory reports.
- Ascertainment of deaths.
- De-duplication of records -- both intrastate and interstate.
- Assessment of missing data.
What increases a surveillance program's ability to estimate viral
- Having a policy in place that requires reporting of all VL test
results to the HIV surveillance program.
- Having access to all HIV surveillance data on a well-defined
- Using common definitions of VL measures.
- Having complete and accurate surveillance and health data.
- Retaining high HIV testing rates.
- Sustaining high linkage to, and retention in, care rates.
- Maintaining high level of collaboration across, and the
functional effectiveness of, policy, care and treatment, and
- Fostering strong relationship with laboratories, particularly
regarding the inflow of data, and promoting policies for reporting
VLs to surveillance systems.
Current Challenges in Calculating Viral Load Measures
- Some states do not have laws/regulations in place for
laboratories to report all VL results.
- Some states do not have the technological or human-resource
ability to enter/import all laboratory information into surveillance
system (e.g., results reside on paper or in a supplementary
- Some laboratories in private or federal hospitals and clinics do
not report HIV lab results to surveillance programs.
- Some states may not receive laboratory reports for a person who
resides in the jurisdiction but receives care in another
jurisdiction (e.g., resident of State A receives HIV care in State
B; State B receives all lab results from clinic in State B, but
those lab results are not reported to State A).
- Some HIV-infected persons are not engaged in ongoing care for
their HIV disease.
- Completeness and accuracy of current address information is
variable in some surveillance systems.
CDC Activities to Address Challenges in Calculating Viral Load Measures
- Supplemental HIV Surveillance Funding
- Awarded supplemental funding ($5.6 million in FY 2010 and
$7.2 million in FY 2011) to HIV surveillance jurisdictions to
support the implementation and maintenance of electronic lab
reporting for all HIV-related test results, as well as importing
of results into the HIV surveillance database.
- Awarded supplemental funding (~$1 million in FY 2010 and
~$1.2 million in FY 2011) to support jurisdictions for geocoding
(determining associated geographic coordinates from geographic
data such as street addresses or ZIP codes) of HIV surveillance
- In collaboration with the Health Resources and Services
Administration, HIV/AIDS Bureau, sponsored a Consultation on Monitoring
and Use of Laboratory Data Reported to HIV Surveillance in March 2011.
- In collaboration with state and local HIV programs, developed
technical guidance on calculating VL measures and released guidance
to HIV surveillance coordinators in August 2011.
- Developing SAS programs to assist state and local HIV
surveillance programs with calculating VL measures; these are
scheduled for release in early 2012.
- National HIV/AIDS Strategy.
Accessed January 30, 2012.
- Centers for Disease Control and Prevention, National
Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Division of
HIV/AIDS Prevention, HIV Incidence and Case Surveillance Branch.
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